1. Field of the Invention
The present invention relates to a printed circuit board, a printed circuit board assembly sheet and a method of manufacturing the same.
2. Description of the Background Art
Actuators are employed in drives such as hard disk drives. Such an actuator includes an arm arranged rotatably with respect to a rotation shaft and a suspension board with circuit for a magnetic head that is attached to the arm. The suspension board with the circuit is a printed circuit board for positioning the magnetic head with a desired track of a magnetic disk.
In manufacturing steps of such a suspension board with circuit, a plurality of suspension boards with circuits are integrally prepared as a suspension board assembly sheet with circuits. In the suspension board assembly sheet with circuits, a plurality of suspension boards with circuits are provided in alignment within a rectangular support frame. After that, each suspension board with circuit is separated from the suspension board assembly sheet with circuits.
In the foregoing manufacturing steps, it is determined whether or not each suspension board with circuit is acceptable by a continuity test or the like before each suspension board with circuit is separated from the suspension board assembly sheet with circuits. The suspension board with circuit determined as a defective item in the foregoing determination is marked using ink or the like. Thus, it can be easily determined whether or not each suspension board with circuit is acceptable in the following step.
In the suspension board assembly sheet with circuits described in JP 2010-161302 A, for example, each suspension board with circuit is provided with a determination mark formation portion. Each suspension board with circuit is configured such that a conductor pattern is formed on a metal support layer with a base insulating layer sandwiched therebetween. In this case, the determination mark formation portion is provided on one surface of the metal support layer, and an opening is provided in the base insulating layer such that the determination mark formation portion is exposed. Ink is applied to the determination mark formation portion of the suspension board with circuit determined as a defective item. Thus, it can be determined whether or not each suspension board with circuit is acceptable in the following step based on whether or not the ink is applied to the determination mark formation portion.
Determination as to whether or not the suspension board with circuit is acceptable needs to be made in various situations. For example, when the actuator of the hard disk does not perform normal operation, it needs to determine whether or not the suspension board with circuit attached to the arm is acceptable in order to confirm that there is no problem in the suspension board with circuit.
In the suspension board assembly sheet with circuits described in JP 2010-161302 A, the determination mark formation portion needs to be confirmed from the side of one surface of the suspension board with circuit in order to determine whether or not the suspension board with circuit is acceptable. Therefore, it is difficult to determine whether or not the suspension board with circuit is acceptable when the one surface of the suspension board with circuit is hid by the arm of the actuator, for example.